1. Field of the Invention
The present invention relates to optical disc devices capable of recording and/or reading data by irradiating a laser beam on an optical disc, and, more particularly, relates to an optical head for irradiating a laser beam on the aforementioned optical disc.
2. Description of the Related Art
As recording media of information such as video, audio or the like, optical discs capable of recording and/or reading information by irradiating a laser beam are used. As the aforementioned optical discs, a compact disc (referred to as CD), a digital versatile disc (referred to as DVD) or the like are widely used. Such optical discs are used as recording media, and an optical disc device for recording data on the optical disc and/or reading data from the optical disc includes an optical head, which records data by irradiating a laser beam on the recording surface of the optical disc and reading data by detecting reflected light.
FIG. 2 shows an arrangement view of an optical head. While the optical head shown in FIG. 2 is not limited to this arrangement, illustrated here is a read-only optical head for reading data recorded on an optical disc. As shown in FIG. 2, the optical head has a laser light source Ld, a grating Gr for forming a laser beam irradiated by a laser light source Ld to three beams, a mirror Mr, a collimator lens Lc, an objective lens Lb, a half mirror Hm, and a light receiving element Pd. The laser beam irradiated by the laser light source Ld is formed to three beams by the grating Gr and reflected by the mirror Mr and to be made incident on the collimator lens Lc. The laser beam incident on the collimator lens Lc is emitted as parallel light and is made incident on the objective lens Lb. The laser beam incident on the objective lens Lb is irradiated on the recording surface of an optical disc Ds.
At this time, the laser beam is converged on a recording layer of the optical disc Ds and is irradiated so that the optical axis is perpendicular to the recording layer of the optical disc Ds. The half mirror Hm is a mirror by which a half of the laser beam incident is transmitted and the remaining half is reflected; and is for guiding the reflected light by the optical disc Ds to the light receiving element Pd. The light receiving element Pd is for converting light to current and for reading data according to light intensity.
FIG. 8A shows a bottom view of a known optical head and FIG. 8B shows a side view of the optical head shown in FIG. 8A. An optical head B shown in FIG. 8A and FIG. 8B is provided with a base 91, a laser light source unit 92 mounted on the base 91, a grating Gr for diffracting a laser beam, and a cover member 93 for radiating heat emitted from the laser light source unit 92.
The base 91 has a light source installation portion 911 for arranging the laser light source unit 92; and two each of internal thread holes 912 disposed in a diagonal line and bosses 913 disposed in a diagonal line different from the line in which the internal thread holes 912 are formed, are formed in the light source installation portion 911. Furthermore, an internal thread hole 914 is also formed on the bottom surface of the base 91.
The laser light source unit 92 has a laser light source Ld and a laser holder 922. The laser light source Ld is fixed by press-fitting to a through hole formed on the laser holder 922.
The cover member 93 is one which is mounted to the bottom surface of the base 91 and has a cover portion 931 for covering the bottom surface and a laser light source holding portion 932 for holding in contact with the laser light source unit 92. The cover member 93 has a grating adjustment window 934 for adjusting the grating Gr and an inclination adjustment window 935 for adjusting inclination of an act base 94 that holds an objective lens.
The laser holder 922 press-fitted with a laser light source Ld is arranged in the light source installation portion 911. At this time, the boss 913 of the light source installation portion 911 is arranged so as to pass through a boss hole of the laser holder 922. By being arranged in such a manner, positioning of the laser holder 922 can be performed.
Further, the cover member 93 is mounted so that the boss 913 passed through the laser holder 922 is close-fitted into the boss hole formed in the laser light source holding portion 932 of the cover member 93.
The laser holder 922 and the cover member 93 can be fixed by inserting a bolt Bt from above the cover member 93 to screw in the internal thread hole 912. Tightening behavior of the bolt Bt is adjusted, thereby performing fine adjustment of the angle of the laser light source unit 92 and performing adjustment of the laser light source Ld.
The invention disclosed in Japanese Unexamined Patent Publication No. 2004-348877 shows that an elastically deforming portion is provided on a heatsink and a laser diode and the aforementioned heatsink are thermally coupled to increase heat radiation capacity.
However, a laser holder Lh for press-fitting the laser light source Ld is a metal molded product and needs a complicated process; therefore, equipment for manufacturing the laser holder Lh is required and much time and trouble in processing are required.
Furthermore, when the laser light source Ld is mounted on the laser holder Lh, the laser light source Ld is mainly fixed by press-fitting to a hole provided in the laser holder Lh. When the laser light source Ld is fixed by press-fitting, an unreasonable force is often applied to the laser light source Ld. If an unreasonable force is applied to the laser light source Ld, an emitting unit of the laser beam is subject to face toward an unexpected direction and the laser light source Ld is subject to damage or breakage.
Furthermore, in the case of the invention disclosed in Japanese Unexamined Patent Publication No. 2004-348877, the elastically deforming portion coming in contact with the laser diode needs to be provided, process of the heatsink is complicated, and consequently much time and trouble are required.